Replicating in virtual desktop infrastructure

ABSTRACT

In one aspect, a method includes determining whether a volume selected for replication is a linked clone, determining if a base file associated with the linked clone exists at a replication site and generating the base file associated with the linked clone at the replication site if a base file does not exist at the replication site.

BACKGROUND

Computer data is vital to today's organizations and a significant partof protection against disasters is focused on data protection. Assolid-state memory has advanced to the point where cost of memory hasbecome a relatively insignificant factor, organizations can afford tooperate with systems that store and process terabytes of data.

Conventional data protection systems include tape backup drives, forstoring organizational production site data on a periodic basis. Anotherconventional data protection system uses data replication, by creating acopy of production site data of an organization on a secondary backupstorage system, and updating the backup with changes. The backup storagesystem may be situated in the same physical location as the productionstorage system, or in a physically remote location. Data replicationsystems generally operate either at the application level, at the filesystem level, or at the data block level.

SUMMARY

In one aspect, a method includes determining whether a volume selectedfor replication is a linked clone, determining if a base file associatedwith the linked clone exists at a replication site and generating thebase file associated with the linked clone at the replication site if abase file does not exist at the replication site.

In another aspect, an apparatus includes electronic hardware circuitryconfigured to determine whether a volume selected for replication is alinked clone, determine if a base file associated with the linked cloneexists at a replication site and generate the base file associated withthe linked clone at the replication site if a base file does not existat the replication site.

In a further aspect, an article includes a non-transitorycomputer-readable medium that stores computer-executable instructions.The instructions cause a machine to determine whether a volume selectedfor replication is a linked clone, determine if a base file associatedwith the linked clone exists at a replication site and generate the basefile associated with the linked clone at the replication site if a basefile does not exist at the replication site.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example of a data protection system.

FIG. 2 is an illustration of an example of a journal history of writetransactions for a storage system.

FIG. 3 is a block diagram of another example of the data protectionsystem.

FIG. 4 is a flowchart of an example of a process to replicate a virtualdesktop infrastructure (VDI).

FIG. 5 is a simplified block diagram of an example of a computer onwhich any of the process of FIG. 4 may be implemented.

DETAILED DESCRIPTION

Described herein are techniques to replicate a virtual desktopinfrastructure (VDI).

The following definitions may be useful in understanding thespecification and claims.

BACKUP SITE—a facility where replicated production site data is stored;the backup site may be located in a remote site or at the same locationas the production site;

BOOKMARK—a bookmark is metadata information stored in a replicationjournal which indicates a point in time.

DATA PROTECTION APPLIANCE (DPA)—a computer or a cluster of computersresponsible for data protection services including inter alia datareplication of a storage system, and journaling of I/O requests issuedby a host computer to the storage system;

HOST—at least one computer or networks of computers that runs at leastone data processing application that issues I/O requests to one or morestorage systems; a host is an initiator with a SAN;

HOST DEVICE—an internal interface in a host, to a logical storage unit;

IMAGE—a copy of a logical storage unit at a specific point in time;

INITIATOR—a node in a SAN that issues I/O requests;

I/O REQUEST—an input/output request (sometimes referred to as an I/O),which may be a read I/O request (sometimes referred to as a read requestor a read) or a write I/O request (sometimes referred to as a writerequest or a write);

JOURNAL—a record of write transactions issued to a storage system; usedto maintain a duplicate storage system, and to roll back the duplicatestorage system to a previous point in time;

LOGICAL UNIT—a logical entity provided by a storage system for accessingdata from the storage system. The logical disk may be a physical logicalunit or a virtual logical unit;

LUN—a logical unit number for identifying a logical unit;

PHYSICAL LOGICAL UNIT—a physical entity, such as a disk or an array ofdisks, for storing data in storage locations that can be accessed byaddress;

PRODUCTION SITE—a facility where one or more host computers run dataprocessing applications that write data to a storage system and readdata from the storage system;

REMOTE ACKNOWLEDGEMENTS—an acknowledgement from remote DPA to the localDPA that data arrived at the remote DPA (either to the appliance or thejournal)

SPLITTER ACKNOWLEDGEMENT—an acknowledgement from a DPA to the protectionagent (splitter) that data has been received at the DPA; this may beachieved by an SCSI (Small Computer System Interface) status command.

SAN—a storage area network of nodes that send and receive an I/O andother requests, each node in the network being an initiator or a target,or both an initiator and a target;

SOURCE SIDE—a transmitter of data within a data replication workflow,during normal operation a production site is the source side; and duringdata recovery a backup site is the source side, sometimes called aprimary side;

STORAGE SYSTEM—a SAN entity that provides multiple logical units foraccess by multiple SAN initiators

TARGET—a node in a SAN that replies to I/O requests;

TARGET SIDE—a receiver of data within a data replication workflow;during normal operation a back site is the target side, and during datarecovery a production site is the target side, sometimes called asecondary side;

THIN PROVISIONING—thin provisioning involves the allocation of physicalstorage when it is needed rather than allocating the entire physicalstorage in the beginning. Thus, use of thin provisioning is known toimprove storage utilization.

THIN LOGICAL UNIT—a thin logical unit is a logical unit that uses thinprovisioning;

VIRTUAL LOGICAL UNIT—a virtual storage entity which is treated as alogical unit by virtual machines;

WAN—a wide area network that connects local networks and enables them tocommunicate with one another, such as the Internet.

A description of journaling and some techniques associated withjournaling may be described in the patent titled “METHODS AND APPARATUSFOR OPTIMAL JOURNALING FOR CONTINUOUS DATA REPLICATION” and with U.S.Pat. No. 7,516,287, which is hereby incorporated by reference.

Referring to FIG. 1, a data protection system 100 includes two sites;Site I, which is a production site, and Site II, which is a backup siteor replica site. Under normal operation the production site is thesource side of system 100, and the backup site is the target side of thesystem. The backup site is responsible for replicating production sitedata. Additionally, the backup site enables roll back of Site I data toan earlier pointing time, which may be used in the event of datacorruption of a disaster, or alternatively in order to view or to accessdata from an earlier point in time.

FIG. 1 is an overview of a system for data replication of eitherphysical or virtual logical units. Thus, one of ordinary skill in theart would appreciate that in a virtual environment a hypervisor, in oneexample, would consume logical units and generate a distributed filesystem on them such as VMFS creates files in the file system and exposethe files as logical units to the virtual machines (each VMDK is seen asa SCSI device by virtual hosts). In another example, the hypervisorconsumes a network based file system and exposes files in the NFS asSCSI devices to virtual hosts.

During normal operations, the direction of replicate data flow goes fromsource side to target side. It is possible, however, for a user toreverse the direction of replicate data flow, in which case Site Istarts to behave as a target backup site, and Site II starts to behaveas a source production site. Such change of replication direction isreferred to as a “failover”. A failover may be performed in the event ofa disaster at the production site, or for other reasons. In some dataarchitectures, Site I or Site II behaves as a production site for aportion of stored data, and behaves simultaneously as a backup site foranother portion of stored data. In some data architectures, a portion ofstored data is replicated to a backup site, and another portion is not.

The production site and the backup site may be remote from one another,or they may both be situated at a common site, local to one another.Local data protection has the advantage of minimizing data lag betweentarget and source, and remote data protection has the advantage is beingrobust in the event that a disaster occurs at the source side.

The source and target sides communicate via a wide area network (WAN)128, although other types of networks may be used.

Each side of system 100 includes three major components coupled via astorage area network (SAN); namely, (i) a storage system, (ii) a hostcomputer, and (iii) a data protection appliance (DPA). Specifically withreference to FIG. 1, the source side SAN includes a source host computer104, a source storage system 108, and a source DPA 112. Similarly, thetarget side SAN includes a target host computer 116, a target storagesystem 120, and a target DPA 124. As well, the protection agent(sometimes referred to as a splitter) may run on the host, or on thestorage, or in the network or at a hypervisor level, and that DPAs areoptional and DPA code may run on the storage array too, or the DPA 124may run as a virtual machine.

Generally, a SAN includes one or more devices, referred to as “nodes”. Anode in a SAN may be an “initiator” or a “target”, or both. An initiatornode is a device that is able to initiate requests to one or more otherdevices; and a target node is a device that is able to reply torequests, such as SCSI commands, sent by an initiator node. A SAN mayalso include network switches, such as fiber channel switches. Thecommunication links between each host computer and its correspondingstorage system may be any appropriate medium suitable for data transfer,such as fiber communication channel links.

The host communicates with its corresponding storage system using smallcomputer system interface (SCSI) commands.

System 100 includes source storage system 108 and target storage system120. Each storage system includes physical storage units for storingdata, such as disks or arrays of disks. Typically, storage systems 108and 120 are target nodes. In order to enable initiators to send requeststo storage system 108, storage system 108 exposes one or more logicalunits (LU) to which commands are issued. Thus, storage systems 108 and120 are SAN entities that provide multiple logical units for access bymultiple SAN initiators.

Logical units are a logical entity provided by a storage system, foraccessing data stored in the storage system. The logical unit may be aphysical logical unit or a virtual logical unit. A logical unit isidentified by a unique logical unit number (LUN). Storage system 108exposes a logical unit 136, designated as LU A, and storage system 120exposes a logical unit 156, designated as LU B.

LU B is used for replicating LU A. As such, LU B is generated as a copyof LU A. In one embodiment, LU B is configured so that its size isidentical to the size of LU A. Thus, for LU A, storage system 120 servesas a backup for source side storage system 108. Alternatively, asmentioned hereinabove, some logical units of storage system 120 may beused to back up logical units of storage system 108, and other logicalunits of storage system 120 may be used for other purposes. Moreover,there is symmetric replication whereby some logical units of storagesystem 108 are used for replicating logical units of storage system 120,and other logical units of storage system 120 are used for replicatingother logical units of storage system 108.

System 100 includes a source side host computer 104 and a target sidehost computer 116. A host computer may be one computer, or a pluralityof computers, or a network of distributed computers, each computer mayinclude inter alia a conventional CPU, volatile and non-volatile memory,a data bus, an I/O interface, a display interface and a networkinterface. Generally a host computer runs at least one data processingapplication, such as a database application and an e-mail server.

Generally, an operating system of a host computer creates a host devicefor each logical unit exposed by a storage system in the host computerSAN. A host device is a logical entity in a host computer, through whicha host computer may access a logical unit. Host device 104 identifies LUA and generates a corresponding host device 140, designated as Device A,through which it can access LU A. Similarly, host computer 116identifies LU B and generates a corresponding device 160, designated asDevice B.

In the course of continuous operation, host computer 104 is a SANinitiator that issues I/O requests (write/read operations) through hostdevice 140 to LU A using, for example, SCSI commands. Such requests aregenerally transmitted to LU A with an address that includes a specificdevice identifier, an offset within the device, and a data size. Offsetsare generally aligned to 512 byte blocks. The average size of a writeoperation issued by host computer 104 may be, for example, 10 kilobytes(KB); i.e., 20 blocks. For an I/O rate of 50 megabytes (MB) per second,this corresponds to approximately 5,000 write transactions per second.

System 100 includes two data protection appliances, a source side DPA112 and a target side DPA 124. A DPA performs various data protectionservices, such as data replication of a storage system, and journalingof I/O requests issued by a host computer to source side storage systemdata. As explained in detail herein, when acting as a target side DPA, aDPA may also enable roll back of data to an earlier point in time, andprocessing of rolled back data at the target site. Each DPA 112 and 124is a computer that includes inter alia one or more conventional CPUs andinternal memory.

For additional safety precaution, each DPA is a cluster of suchcomputers. Use of a cluster ensures that if a DPA computer is down, thenthe DPA functionality switches over to another computer. The DPAcomputers within a DPA cluster communicate with one another using atleast one communication link suitable for data transfer via fiberchannel or IP based protocols, or such other transfer protocol. Onecomputer from the DPA cluster serves as the DPA leader. The DPA clusterleader coordinates between the computers in the cluster, and may alsoperform other tasks that require coordination between the computers,such as load balancing.

In the architecture illustrated in FIG. 1, DPA 112 and DPA 124 arestandalone devices integrated within a SAN. Alternatively, each of DPA112 and DPA 124 may be integrated into storage system 108 and storagesystem 120, respectively, or integrated into host computer 104 and hostcomputer 116, respectively. Both DPAs communicate with their respectivehost computers through communication lines such as fiber channels using,for example, SCSI commands or any other protocol.

DPAs 112 and 124 are configured to act as initiators in the SAN; i.e.,they can issue I/O requests using, for example, SCSI commands, to accesslogical units on their respective storage systems. DPA 112 and DPA 124are also configured with the necessary functionality to act as targets;i.e., to reply to I/O requests, such as SCSI commands, issued by otherinitiators in the SAN, including inter alia their respective hostcomputers 104 and 116. Being target nodes, DPA 112 and DPA 124 maydynamically expose or remove one or more logical units.

As described hereinabove, Site I and Site II may each behavesimultaneously as a production site and a backup site for differentlogical units. As such, DPA 112 and DPA 124 may each behave as a sourceDPA for some logical units, and as a target DPA for other logical units,at the same time.

Host computer 104 and host computer 116 include protection agents 144and 164, respectively. Protection agents 144 and 164 intercept SCSIcommands issued by their respective host computers, via host devices tological units that are accessible to the host computers. A dataprotection agent may act on an intercepted SCSI commands issued to alogical unit, in one of the following ways: send the SCSI commands toits intended logical unit; redirect the SCSI command to another logicalunit; split the SCSI command by sending it first to the respective DPA;after the DPA returns an acknowledgement, send the SCSI command to itsintended logical unit; fail a SCSI command by returning an error returncode; and delay a SCSI command by not returning an acknowledgement tothe respective host computer.

A protection agent may handle different SCSI commands, differently,according to the type of the command. For example, a SCSI commandinquiring about the size of a certain logical unit may be sent directlyto that logical unit, while a SCSI write command may be split and sentfirst to a DPA associated with the agent. A protection agent may alsochange its behavior for handling SCSI commands, for example as a resultof an instruction received from the DPA.

Specifically, the behavior of a protection agent for a certain hostdevice generally corresponds to the behavior of its associated DPA withrespect to the logical unit of the host device. When a DPA behaves as asource site DPA for a certain logical unit, then during normal course ofoperation, the associated protection agent splits I/O requests issued bya host computer to the host device corresponding to that logical unit.Similarly, when a DPA behaves as a target device for a certain logicalunit, then during normal course of operation, the associated protectionagent fails I/O requests issued by host computer to the host devicecorresponding to that logical unit.

Communication between protection agents and their respective DPAs mayuse any protocol suitable for data transfer within a SAN, such as fiberchannel, or SCSI over fiber channel. The communication may be direct, orvia a logical unit exposed by the DPA. Protection agents communicatewith their respective DPAs by sending SCSI commands over fiber channel.

Protection agents 144 and 164 are drivers located in their respectivehost computers 104 and 116. Alternatively, a protection agent may alsobe located in a fiber channel switch, or in any other device situated ina data path between a host computer and a storage system or on thestorage system itself. In a virtualized environment, the protectionagent may run at the hypervisor layer or in a virtual machine providinga virtualization layer.

What follows is a detailed description of system behavior under normalproduction mode, and under recovery mode.

In production mode DPA 112 acts as a source site DPA for LU A. Thus,protection agent 144 is configured to act as a source side protectionagent; i.e., as a splitter for host device A. Specifically, protectionagent 144 replicates SCSI I/O write requests. A replicated SCSI I/Owrite request is sent to DPA 112. After receiving an acknowledgementfrom DPA 124, protection agent 144 then sends the SCSI I/O write requestto LU A. After receiving a second acknowledgement from storage system108 host computer 104 acknowledges that an I/O command complete.

When DPA 112 receives a replicated SCSI write request from dataprotection agent 144, DPA 112 transmits certain I/O informationcharacterizing the write request, packaged as a “write transaction”,over WAN 128 to DPA 124 on the target side, for journaling and forincorporation within target storage system 120.

DPA 112 may send its write transactions to DPA 124 using a variety ofmodes of transmission, including inter alia (i) a synchronous mode, (ii)an asynchronous mode, and (iii) a snapshot mode. In synchronous mode,DPA 112 sends each write transaction to DPA 124, receives back anacknowledgement from DPA 124, and in turns sends an acknowledgement backto protection agent 144. Protection agent 144 waits until receipt ofsuch acknowledgement before sending the SCSI write request to LU A.

In asynchronous mode, DPA 112 sends an acknowledgement to protectionagent 144 upon receipt of each I/O request, before receiving anacknowledgement back from DPA 124.

In snapshot mode, DPA 112 receives several I/O requests and combinesthem into an aggregate “snapshot” of all write activity performed in themultiple I/O requests, and sends the snapshot to DPA 124, for journalingand for incorporation in target storage system 120. In snapshot mode DPA112 also sends an acknowledgement to protection agent 144 upon receiptof each I/O request, before receiving an acknowledgement back from DPA124.

For the sake of clarity, the ensuing discussion assumes that informationis transmitted at write-by-write granularity.

While in production mode, DPA 124 receives replicated data of LU A fromDPA 112, and performs journaling and writing to storage system 120. Whenapplying write operations to storage system 120, DPA 124 acts as aninitiator, and sends SCSI commands to LU B.

During a recovery mode, DPA 124 undoes the write transactions in thejournal, so as to restore storage system 120 to the state it was at, atan earlier time.

As described hereinabove, LU B is used as a backup of LU A. As such,during normal production mode, while data written to LU A by hostcomputer 104 is replicated from LU A to LU B, host computer 116 shouldnot be sending I/O requests to LU B. To prevent such I/O requests frombeing sent, protection agent 164 acts as a target site protection agentfor host Device B and fails I/O requests sent from host computer 116 toLU B through host Device B.

Target storage system 120 exposes a logical unit 176, referred to as a“journal LU”, for maintaining a history of write transactions made to LUB, referred to as a “journal”. Alternatively, journal LU 176 may bestriped over several logical units, or may reside within all of or aportion of another logical unit. DPA 124 includes a journal processor180 for managing the journal.

Journal processor 180 functions generally to manage the journal entriesof LU B. Specifically, journal processor 180 enters write transactionsreceived by DPA 124 from DPA 112 into the journal, by writing them intothe journal LU, reads the undo information for the transaction from LUB. updates the journal entries in the journal LU with undo information,applies the journal transactions to LU B, and removes already-appliedtransactions from the journal.

Referring to FIG. 2, which is an illustration of a write transaction 200for a journal. The journal may be used to provide an adaptor for accessto storage 120 at the state it was in at any specified point in time.Since the journal contains the “undo” information necessary to roll backstorage system 120, data that was stored in specific memory locations atthe specified point in time may be obtained by undoing writetransactions that occurred subsequent to such point in time.

Write transaction 200 generally includes the following fields: one ormore identifiers; a time stamp, which is the date & time at which thetransaction was received by source side DPA 112; a write size, which isthe size of the data block; a location in journal LU 176 where the datais entered; a location in LU B where the data is to be written; and thedata itself.

Write transaction 200 is transmitted from source side DPA 112 to targetside DPA 124. As shown in FIG. 2, DPA 124 records the write transaction200 in the journal that includes four streams. A first stream, referredto as a DO stream, includes new data for writing in LU B. A secondstream, referred to as an DO METADATA stream, includes metadata for thewrite transaction, such as an identifier, a date & time, a write size, abeginning address in LU B for writing the new data in, and a pointer tothe offset in the DO stream where the corresponding data is located.Similarly, a third stream, referred to as an UNDO stream, includes olddata that was overwritten in LU B; and a fourth stream, referred to asan UNDO METADATA, include an identifier, a date & time, a write size, abeginning address in LU B where data was to be overwritten, and apointer to the offset in the UNDO stream where the corresponding olddata is located.

In practice each of the four streams holds a plurality of writetransaction data. As write transactions are received dynamically bytarget DPA 124, they are recorded at the end of the DO stream and theend of the DO METADATA stream, prior to committing the transaction.During transaction application, when the various write transactions areapplied to LU B, prior to writing the new DO data into addresses withinthe storage system, the older data currently located in such addressesis recorded into the UNDO stream. In some examples, the metadata stream(e.g., UNDO METADATA stream or the DO METADATA stream) and the datastream (e.g., UNDO stream or DO stream) may be kept in a single streameach (i.e., one UNDO data and UNDO METADATA stream and one DO data andDO METADATA stream) by interleaving the metadata into the data stream.

Referring to FIG. 3, the data replication system 100 in FIG. 1 may bemodified to be used in replicating in VDI. For example, a datareplication system 300 may be used to replicate in VDI. VDI is adesktop-centric service that hosts a user desktop environment on one ormore servers (e.g., remote servers). Typically, the desktop-centricservice is accessed over a network using a remote display protocol, forexample, and a connection brokering service is used to connect users totheir assigned desktop sessions. Thus, a user may access their desktopfrom any location, without being tied to a single client device (e.g.,one PC). Since the resources are centralized, users may change workaccess locations but still be capable of accessing the same desktopenvironment with their applications and data. Typically, a VDI base fileis kept with the centralized resources and each user has an individualVDI volume with their applications and data. That is, VDI volumes arelinked clones that have a joint parent, VDI base file

The data replication system 300 includes, at a production site, ahypervisor 302 a, a Virtual Machine File System (VMFS) 330, a storagearray 304 with a logical unit 328 and a hypervisor 302 b and, at areplication site, a hypervisor 302 b, a VMFS 340 and a storage array344. The hypervisor 302 a includes virtual machines (VMs) (e.g., a VMs342 a, a VM 342 b, and a VM 342 c), a DPA 310 a and a splitter 322(similar to the data protection agent 144 in FIG. 1 for example). TheDPA 310 a includes a VDI replicator 320 that controls replication ofVDI. The VMFS 330 includes a VDI base file 310, a first VDI volume 316a, a second VDI volume 316 b and a third VDI volume 316 c. The VDI VMs342 a-342 c use volumes 316 a-316 c, respectively, which are linkedclones.

Referring to FIG. 4, an example of a process to replicate VDI is aprocess 400 performed by the VDI replicator 320, for example. Process400 determines whether a volume to be replicated is a linked clone in aVDI (402). For example, VDI replicator 320 determines if a first VDIvolume 316 a is a linked clone. If the volume is a linked clone, process400 determines if a base file exists at the replication site (406). Forexample, VDI replicator, 320 determines if a base file is at the VMFS340.

If the base file does not exist at the replication site, process 400generates a VDI base file at the replica site (410) and copies the basefile from the production site to the replica site (412). For example,the VDI replicator 320 generates a base file 350 at the VMFS 340 andcopies data from the VDI base file 310 to the base file 350.

Process 400 generates linked clone of the volumes at the replica site(414). For example, the VDI replicator 320 generates VDI volumes 356a-356 c at the VMFS 340.

Process 400 replicates data from the VDI volumes at the production siteto the replication site (418). For example, data from the VDI volumes316 a-316 c, not in the VDI base file 310, are copied to the VDI volumes356 a-356 c, respectively. While some VDI volumes may be replicated notall VDI linked clones are replicated. For example, if only VDI volume316 a is chosen to be replicated, then only VDI volume 356 a will begenerated at the target site.

Referring to FIG. 5, in one example, the VDI replicator 320 is a VDIreplicator 320′. The VDI replicator 320′ includes a processor 502, avolatile memory 504, a non-volatile memory 506 (e.g., hard disk) and theuser interface (UI) 508 (e.g., a graphical user interface, a mouse, akeyboard, a display, touch screen and so forth). The non-volatile memory506 stores computer instructions 512, an operating system 516 and data518. In one example, the computer instructions 512 are executed by theprocessor 502 out of volatile memory 504 to perform all or part of theprocesses described herein (e.g., process 400).

The processes described herein (e.g., process 400) are not limited touse with the hardware and software of FIG. 5; they may findapplicability in any computing or processing environment and with anytype of machine or set of machines that is capable of running a computerprogram. The processes described herein may be implemented in hardware,software, or a combination of the two. The processes described hereinmay be implemented in computer programs executed on programmablecomputers/machines that each includes a processor, a non-transitorymachine-readable medium or other article of manufacture that is readableby the processor (including volatile and non-volatile memory and/orstorage elements), at least one input device, and one or more outputdevices. Program code may be applied to data entered using an inputdevice to perform any of the processes described herein and to generateoutput information.

The system may be implemented, at least in part, via a computer programproduct, (e.g., in a non-transitory machine-readable storage medium suchas, for example, a non-transitory computer-readable medium), forexecution by, or to control the operation of, data processing apparatus(e.g., a programmable processor, a computer, or multiple computers)).Each such program may be implemented in a high level procedural orobject-oriented programming language to communicate with a computersystem. However, the programs may be implemented in assembly or machinelanguage. The language may be a compiled or an interpreted language andit may be deployed in any form, including as a stand-alone program or asa module, component, subroutine, or other unit suitable for use in acomputing environment. A computer program may be deployed to be executedon one computer or on multiple computers at one site or distributedacross multiple sites and interconnected by a communication network. Acomputer program may be stored on a non-transitory machine-readablemedium that is readable by a general or special purpose programmablecomputer for configuring and operating the computer when thenon-transitory machine-readable medium is read by the computer toperform the processes described herein. For example, the processesdescribed herein may also be implemented as a non-transitorymachine-readable storage medium, configured with a computer program,where upon execution, instructions in the computer program cause thecomputer to operate in accordance with the processes. A non-transitorymachine-readable medium may include but is not limited to a hard drive,compact disc, flash memory, non-volatile memory, volatile memory,magnetic diskette and so forth but does not include a transitory signalper se.

The processes described herein are not limited to the specific examplesdescribed. For example, the process 400 is not limited to the specificprocessing order of FIG. 4. Rather, any of the processing blocks of FIG.4 may be re-ordered, combined or removed, performed in parallel or inserial, as necessary, to achieve the results set forth above.

The processing blocks (for example, in the process 400) associated withimplementing the system may be performed by one or more programmableprocessors executing one or more computer programs to perform thefunctions of the system. All or part of the system may be implementedas, special purpose logic circuitry (e.g., an FPGA (field-programmablegate array) and/or an ASIC (application-specific integrated circuit)).All or part of the system may be implemented using electronic hardwarecircuitry that include electronic devices such as, for example, at leastone of a processor, a memory, a programmable logic device or a logicgate.

Elements of different embodiments described herein may be combined toform other embodiments not specifically set forth above. Otherembodiments not specifically described herein are also within the scopeof the following claims.

What is claimed is:
 1. A method comprising: replicating a virtualdesktop infrastructure (VDI) from a production site to a replicationsite using a replicator stored on a first hypervisor at the productionssite, wherein the first hypervisor is connected to a second hypervisorat the replication site, the replicating comprising: determining whethera first volume, stored on a first virtual machine file system at theproduction site and selected for replication, is a linked clone bydetermining if a second volume stored on the first virtual machine filesystem and the first volume have a first base file that is a jointparent of the first and second volumes, the first virtual machine filesystem connected to the first hypervisor; determining if a second basefile associated with the linked clone exists at a second virtual machinefile system at the replication site if the first volume is a linkedclone, the second virtual machine file system connected to the secondhypervisor; and generating the second base file associated with thelinked clone on the second virtual machine file system at thereplication site if the second base file does not exist at thereplication site.
 2. The method of claim 1, further comprising copyingdata from the first base file associated with the first volume from theproduction site to the second base file at the replication site.
 3. Themethod of claim 2, further comprising generating a linked clone on thesecond virtual machine file system at the replication site for the firstvolume selected to be replicated.
 4. The method of claim 3, furthercomprising replicating data in a linked clone to the linked clone at thereplication site if the data is not in the base file.
 5. The method ofclaim 1, further comprising configuring a first virtual machine storedon the first hypervisor to use the first volume.
 6. The method of claim1, further comprising replicating the second volume at the replicationsite if the second volume is selected for replication.
 7. An apparatus,comprising: electronic hardware circuitry configured to replicate avirtual desktop infrastructure (VDI) from a production site to areplication site using a replicator stored on a first hypervisor at theproductions site, wherein the first hypervisor is connected to a secondhypervisor at the replication site, the circuitry configured toreplicate comprising circuitry to: determine whether a first volume,stored on a first virtual machine file system at the production site andselected for replication, is a linked clone by determining if a secondvolume stored on the first virtual machine file system and the firstvolume have a first base file that is a joint parent of the first andsecond volumes, the first virtual machine file system connected to thefirst hypervisor; determine if a second base file associated with thelinked clone exists at a second virtual machine file system at thereplication site if the first volume is a linked clone, the secondvirtual machine file system connected to the second hypervisor; andgenerate the second base file associated with the linked clone on thesecond virtual machine file system at the replication site if the secondbase file does not exist at the replication site.
 8. The apparatus ofclaim 7, wherein the circuitry comprises at least one of a processor, amemory, a programmable logic device or a logic gate.
 9. The apparatus ofclaim 7, further comprising circuitry configured to copy data from thefirst base file associated with the first volume from the productionsite to the second base file at the replication site.
 10. The apparatusof claim 9, further comprising circuitry configured to generate a linkedclone on the virtual machine file system at the replication site for thefirst volume selected to be replicated.
 11. The apparatus of claim 10,further comprising circuitry configured to replicate data in a linkedclone to the linked clone at the replication site if the data is not inthe base file.
 12. The apparatus of claim 7, further comprisingcircuitry configured to configure a first virtual machine stored on thefirst hypervisor to use the first volume.
 13. The apparatus of claim 7,further comprising circuitry configured to replicate the second volumeat the replication site if the second volume is selected forreplication.
 14. An article comprising: a non-transitorycomputer-readable medium that stores computer-executable instructions toreplicate a virtual desktop infrastructure (VDI) from a production siteto a replication site using a replicator stored on a first hypervisor atthe productions site, wherein the first hypervisor is connected to asecond hypervisor at the replication site, the instructions causing amachine to: determine whether a first volume, stored on a first virtualmachine file system at the production site and selected for replication,is a linked clone by determining if a second volume stored on the firstvirtual machine file system and the first volume have a first base filethat is a joint parent of the first and second volumes, the firstvirtual machine file system connected to the first hypervisor; determineif a second base file associated with the linked clone exists at asecond virtual machine file system at the replication site if the firstvolume is a linked clone, the second virtual machine file systemconnected to the second hypervisor; and generate the second base fileassociated with the linked clone on the second virtual machine filesystem at the replication site if the second base file does not exist atthe replication site.
 15. The article of claim 14, further comprisinginstructions causing the machine to copy data from the first base fileassociated with the first volume from the production site to the secondbase file at the replication site.
 16. The article of claim 15, furthercomprising instructions causing the machine to generate a linked cloneon the virtual machine file system at the replication site for the firstvolume selected to be replicated.
 17. The article of claim 16, furthercomprising instructions causing the machine to replicate data in alinked clone to the linked clone at the replication site if the data isnot in the base file.
 18. The article of claim 14, further comprisinginstructions causing the machine to configure a first virtual machinestored on the first hypervisor to use the first volume.
 19. The articleof claim 14, further comprising instructions causing the machine toreplicate the second volume at the replication site if the second volumeis selected for replication.